1. Field of the Invention
The present invention relates to photoluminescent materials, such as those used in organic light emitting diodes (OLEDs), and particularly to a method of making doped tris(8-hydroxyquinolinato)aluminum (Alq3) nanostructures having enhanced photoluminescence.
2. Description of the Related Art
Tris(8-hydroxyquinolinato)aluminum (Al(C9H6NO)3) is a coordination complex where aluminum is bonded in a bidentate manner to the conjugate base of three 8-hydroxyquinoline ligands. Tris(8-hydroxyquinolinato)aluminum (commonly referred to as Alq3) is a common component of organic light emitting diodes (OLEDs). Variations in the substituents on the quinoline rings affect its luminescence properties. Primarily, Alq3 is used as the material for the electron-transport layer and also as the host for the emitter layer in OLEDs.
The ligand, quinolinolate, has long been used as a complexing agent in a wide variety of analytical techniques. Alq3 is an octahedrally coordinated chelate complex of the type M(NO)3, where M is a trivalent metal and N and O are the nitrogen and oxygen atoms in the bidentate quinolinolate ligand. Because of the bidentate nature of the ligand, the Alq3 complex can occur in two isomeric forms, namely, a facial isomer and a meridional isomer, depending on the orientations of the ligands.
Recently, there has been research on fabricating Alq3 in nanostructure form. For example, Alq3 spherical nanoparticles have been fabricated by vapor condensation, having an average size varying between 50 nm and 500 mm. The photoluminescence (PL) spectra of the nanoparticles showed a broadened peak varying from 450 nm to 700 nm. It was reported that the maximum intensity increased as the particle size decreased, due to the large specific surface area. Other techniques for the manufacture of nano-crystals of Alq3 have been reported, such as through the use of solvents. Additional research has gone into the improvement of the luminescence properties of Alq3 through the addition of other materials, however only very limited improvements have been reported.
At the nanoscale, many properties of Alq3 can be improved, particularly through doping with proper activators. In order to enhance the photoluminescence of Alq3, for use in OLEDs and the like, it would be desirable to efficiently and effectively synthesize doped Alq3, at the nanoscale level, by incorporating different impurities in the host.
Thus, a method of making doped Alq3 nanostructures with enhanced photoluminescence solving the aforementioned problems is desired.